Industrial polluted soil borne fungi decolorize the recalcitrant azo dyes Synozol red HF–6BN and Synozol black B

Today's world needs to control the industrial pollution through smarter ways. Presently, we observed the capacity of soil borne fungi to digest Synozol Red HF–6BN and Synozol Black B. Initially, 86 fungal strains were isolated from soil samples randomly collected from industrial sites. Among these, 31 isolates were capable of dye decolorization on solid media, with SN12f and SN13a isolates showed the highest decolorization capacity. The dye decolorization by both strains was higher (80–95%), when incubated for 120 h under optimized conditions of pH, concentration, nutrient source and temperature. The dye (Synozol red HF–6BN and Synozol black B) decolorization by SN12f isolate was maximum (˃90%) at pH7, whereas the SN13a decolorized 90% of Synozol red HF–6BN and 89% of Synozol black B at pH3. The SN13a and SN12f isolates at 40 mg/L showed de-colorization of 94.71%, 81.4% (for Synozol red HF–6BN) and 90.5%, 84.4% (Synozol black B), respectively. Our isolates also mitigated the toxic effect of azo dyes on the growth of phosphate solubilizing soil bacteria. In fact, the untreated effluent showed toxic effects on the growth of beneficial bacterial by developing zone of inhibition (16.5 mm around Aeromonas spp., 14.5 mm around Sallmonella while 14.25 mm around Citrobacter spp). However, the fungal treated dye was unable to develop zone of inhibition. Laccase activity was positive for both of fungal isolates after incubation on Bassnell Hass Medium (0.0733 U/mL for SN12f and 0.0439 U/mL SN13a). Using molecular approaches (ITS region), SN12f was identified as Aspergillus nidulans, while SN13a as Aspergillus fumigatus. The current study showed that local fungal flora can reclaim the contaminated soils and support the agro-friendly micro-flora. •Degradation of toxic dyes Synozol Red and Synozol black by fungal isolate SN12f.•The fungi SN13a also degraded the Synozol Red and Synozol black efficiently.•Both isolates showed optimum degradation of toxic azo dyes at pH ranges 5–7.•The isolates also supported the growth of phosphate solubilizing soil bacteria.•SN12f was identified as Aspergillus nidulans and SN13a as Aspergillus fumigatus.